GB2505431A

GB2505431A - Downhole tool with drive coupling and torque limiter

Info

Publication number: GB2505431A
Application number: GB1215345.8A
Authority: GB
Inventors: Alan Martyn Eddison; Rory Mccrae Tulloch
Original assignee: NOV Downhole Eurasia Ltd
Current assignee: NOV Downhole Eurasia Ltd
Priority date: 2012-08-29
Filing date: 2012-08-29
Publication date: 2014-03-05
Anticipated expiration: 2032-08-29
Also published as: GB2505431B; MX356034B; WO2014033462A3; GB201215345D0; MX2015002506A; US9909367B2; EA033503B1; EA038550B1; EA201590448A1; AU2013308254B2; WO2014033462A2; US20150226015A1; EA201991631A1; AU2013308254A1

Abstract

A downhole tool coupling for selectively transmitting torque downhole between a drive portion and a rotatable portion, such as between teeth 72 on resilient collet fingers 74 on an outer sleeve 63 and teeth 70 on an inner sleeves 62 of a directional drill drive assembly 26 which are axially alignable with each other to enable adjustment of the orientation of a drill bit, also incorporates a torque limiter. Torque limitation may be achieved by bearing surfaces (75,77, figure 3)between teeth 70,72 having radially offset angles providing non-tangential forces which urge outer sleeve collet teeth 72 outwards, and out of engagement with inner sleeve teeth 70 above a predetermined threshold torque. The collet fingers 74 may extend axially (figure 4) or alternatively extend circumferentially around the outer sleeve (163, figure 7).

Description

DOWNHOLE TOOL WTH ROTATIONAL DRIVE COUPLING AND ASSOCIATED

METHODS

FIELD OF THE INVENTION

The present invention relates to a downhole tool with a rotational drive ccupllng and associated methods; in particular, but not exclusively, to a rotational drive coupllng for selectively rotating a portion of a downhole fool, such as a portion of a directional drilling apparatus.

BACKGROUND TO THE INVENTION

in downhoie operations, such as in bores for reservoirs (e.g. oil and gas reservoirs), downhole tools are often required to be rotated, such as for drilhng the bore.

In some operations rotallon is temporarfly or seectiveIy tranamiffed downhole, For example, in directional or controlled trajectory drilling, a steering portion of the downhole tool may he rotated only when the direction of drilllng is changed; whilst the drill bit may be rotated more of the time.

In directional drilling, the vertical indflnation and azimuth of a drllled bore may be controlled such that the bore may extend from the surface to a target area which is not vertically aligned with the point on the surface where drilling commences. This permits a wide area to be accessed from a single drilling location and is therefore particularly useful in offshore drilhng operations.

Applicantts GB Z343,470 and US Patent Application No, 09/435,453, and also WO9T;4784 and US Patent Application No. 09/202,342 and US Patent Appllcation No, US 10/470,031. the disclosures of which are incorporated herein by reference, describe arrangements including nonrotating off set masses to provide a desired offset of the drill string in the bore.

tn some downhole operations there can be changes in the transmission of rotational drive that result in a driven component being inadvertently coupled or decoupled; or coupled or decoupled under undesirable conditions. For example, where a drive coupllng is controlled by a fluid pressure or a fluid pressure differential, the driven component may be inadvertently coupled by an unplanned change in fluid pressure (e.g. if a pump faUs). Unde&rably tranemitfing drive to components can potenUaHy damage the driven components or other parts of the downhole tool or associated equipment; or cause delay or impede operations.

it is among the objectives of at least one embodiment of at least one aspect of the present invention to seek to obviate or at east mitigate one or more problems and/or disadvantages of the phor art.

SUMMARY OF THE INVENTION

Accorthng to an aspect of the invention there is proded a downhole tool comprising: a rotatable inner sloe-ye comprising an inner sleeve coupng porhon; a rotatable outer sleeve mounted coaxiaUy with the inner sleeve and compri&ng an outer sleeve coupng porlion for engagement with the inner sleeve coupUng porflon for transmitting a torque between the inner and outer sleeves; wherein the tool is reconfigurabie between a first configuration whereby the inner and outer sleeve coupng portions are axiafly misaligned to prevent transmission of torque between the inner and outer sleeves, and a second configuration whereby the inner and outer sleeve coupling portions are axially aligned to permit a transmission of torque between the inner and outer sleeves; and wherein at east one of the inner or outer sleeve couphng porhons is configured to prevent the transmission of torque above a predetermined torque threshold when the tool is in the second configuration.

Providing sue-h a downhole tool may permit the selective transmission of torque within a predetermined torque range. The selective transmission of torque may permit the selective rotation of at least one of the sleeves. Preventing the transmission of torque above a predetermined threshold when the coupling portions are axially aligned may prevent damage to the tool or associated equipment For example, the torque threshold may be determined by a mechanical property (ag. a strength or an impact resistance or the like) of one of the sleeves or a mechanical property of a member connected or associated with one of the sleeves.

At least one of the inner or outer sleeve coupling portions may be configurec to prevent engagement of the coupling portions above the predetermined torque threshold.

At east one of the nner or outer seeve coupng portions may be configured to disengage the coupng portions at the predetermined torque threshod, At east one of the inner or outer seeve couphng portions may be configured lo disengage the other of the outer or inner aeeve coupUng portion on exceeding the predetermined torque thshold.

The inner and outer seeve couphng portions may form a coupHng arrangement for transmitting the torque between the inner and outer sleeves. The coupng arrangement may be interengaging. The coupng arrangement may be configured to rtisplace at least one of the coupng portions in response to the predetermined torque. The coupilng arrangement may be configured to substantiSy rathaHy displace at least one of the coupflng portions in response to the predetermined torque. The coupng arrangement may be configured to substanUay axiaHy displace at east one of the coupng portions in response to (he predetermined torque. The coupUng arrangement may comprise no discrete spring components. For example, (he coupng arrangement may be configured to engage and disengage without a sphng (e.g. a torsional, hScal or co spring). A discrete spring component may provide a potential mechanical weakness and/or a toerance problem and/or a susceptibity to debris irnpedmenL and/or an assembly or repair issue. A cflscrete sphng component may be more prone to tilting or jarring, such as under high impact.

The coupng arrangement may comprise a torque Umiter.

At east one of the inner or outer eeve coupng portions may be configured to convert at least a portion of the torque into a directional force in a direction other than that of rotation. The portion of torque may be a portion of tangential force associated with the torque. The directional force may be a substant.iay non4angential force. The directionai force may be a substantiaHy lateral force. The directional force may be a substantially radial force. At east one of the inner or outer sleeve coupng portions may be configured to convert a predetermined porfion of the torque into a directional force. A magnitude of the directional force may vary proportionately with the torque.

The directional force may comprise a disengaging force at a predetermined magnitude.

The/each coupng portion may comprise a bearing (or drive contact) surface for contacting the other coupng portion to transfer torque between the sleeves. The/each bearing surface may be configured to he substantiaUy transverse to the direction of rotation, The/each bearing surface may be configured to be substantially perpendicur to the direcUon of rotation, The/each bearing surface may be configured to be non perpendicular (e.g. oWperpendicular) to the direction of rotation. The/each bearing surface may be nonperpendicular to the sleeve. The/each bearing surface may be arranged at an offset angle. The offset angle may be relative to a plane perpendicular to the direction of rotation. The offset angle may be relative to a radius of the sleeve.

The offset angle may be restive to a plane defined by a central longitudinal axis of the sleeve and a radius of the &eeve. The offset angle may be predetermined, The offset angle may correspond to a particular torque threshold. The torque threshold may be at least partiay defined by the offset angie. The offset angle may provide for a radial movement of the bearing surface/s at the predetermined torque. The radial movement may be outwards. The radial movement may he inwards. Adthtionally or alternatively, the offset angle may provide for an axial movement of the bearing surface/s at the predetermined torque. The offset angle may be such as to not allow unlimited torque transmission.

The/each coupling portion may be configured to be substantiauy unaffected by a rotational speed, such as a rotational speed within an operational range. For example, the/each coupling portion may be configured to be substantially undefiected or undisplaced by a centrifugal force associated with an operational rotational speed.

Additionally, or alternatively, each coupling portion may be configured to displace or deflect outwards by a similar distance at a same rotational speed. Accordingly. the coupling portions may remain engaged with each other within an operational speed range.

Alternatively, the/each coupling portion may be configured to selectively disengage outwith an operational rotational speed range. For example, one coupng portion may be configured to displace or deflect outwards more than the other coupling portion at a same rotational speed. Accordingly, the coupling porUons may be disengaged outside an operational speed range.

The/each coupng porflon may be configured to transmit torque in only one direction (ag. only clockwise or only counteNcbckwise). The/each coupflng portion may comprise a plurahty of bearing surfaces for transmitting torque in the single direction.

Alternatively, the/each couphng porflon may be configured to transmit torque in more than one direction (ag. clockwise and counter-clockwise). The/each coupling portion may comprise a pluraUty of bearing surfaces for transmitting torque in more than one direction.

The pluraty of bearing surfaces may be thstributed around the respective coupling porflon/s. The distribution may be even (e.g. each bearing surface may be equkiistant in each direction from a next adjacent hearing surface). An even distribution of the pluraty of bearing surfaces may allow for a balanced transmission of torque (e.g. about a central longitudinal axis of the tool).

The bearing surfaces may he configured to slide relative to each other. The bearing surfaces may be conflgured to slide relative to each other at the predetermined torque.

The bearing surfaces may comprise a friction property such thaI the bearing surfaces slide relative to each other at the predetermined torque. The friction property may comprise a coefficient of friction. The friction property may comprise a surface roughness of at least one of the bearing surfaces. The friction property may comprise a surface energy property. The friction property may comprise a lubrication property. The lubrication may be provided by a lubricant. The apparatus may comprise a lubricant reservoir for lubricating the bearing surface/s. The tool may comprise a fluid chamber housing the bearing surfaces. The fluid chamber may house the bearing surfaces in a lubricant oil reservoir. The fluid chamber may be sealed. such as sealed from a drilling fluid and/or a welibore fluid. Alternatively, the lubrication property may be provided by an actuation fluid, such as a drilling fluid. The torque threshold may be at least partially defined by the friction property.

The/each coupling portion may be configured to move relative to a respective sleeve body portion. For example, the outer sleeve coupUng portion may he configured to move substantially radially relative to an outer sleeve body portion.

At least one of the coupng porUons may be fixed relative to the respective sleeve. For example, the inner sleeve coupUng portion may be fixed relative to an inner s!eeve body porfion, At least one of the coupUng portions may comprise a longitudinal element, The longitudinal element may comprise the bearing surtace. The longitudinal element may comprise a long tudin member. The longitudinal element may comprise a finger. The longitudinal element may comprise a coet finger. The longitudinal Sement may comprise a slot. The longitudinal element may comprise a spline.

At least a portion of the longitudinal element may he configured to deflect or displace in a substantially nonaxial direction relative to the sleeve. The longitudinal element may comprise a longitudinal axis in a direction of the longitudinal elements primary dimension. The longitudinal element may be configured to deflect or displace transverse to the &emenVs longitudinal axis. The longitudinal element may be configured to deflect or displace such that the coupling portions disengage. The longitudinal element may be configured to deflect or displace such that the coupling portions disengage at the predetermined torque.

The longitudinal element may he configured to deflect or displace substantially transverse to the iongftudinal axis of the sleeve. The longitudinal element may be configured to deflect or displace substantiafly transverse to the sleeve. The longitudinal element may be configured to deflect or displace substantially radially. The ngitudinal element may be configured to deflect or displace substantiay radiafly at the predetermined torque threshold. The longitudinal element may be resilient. Providing a resilient longitudinal member may permit reengagement of the coupling portions, such as when the torque drops belcw the predetermined threshold. The longitudinal element may be elastic. The longitudinal element may be longitudinaNy arranged relative to the sleeve, such as substantially parallel to the central longitudinal axis ci the sleeve. The longitudinal element may he substantially straight. Alternatively, the longitudinal element may be substantiaily curved in at least one direction. Longitudinally arranging the longitudinal element may permit an increased length of the longitudinal element.

The longäudinal element may be substantially circumferentially arranged, such as substantially around a circumference of the sleeve. Circumferentially arranging the longitudinal element may permit a reduced overall length of the sleeve. The longitudinal Sement may be helically arranged, Helicay arranging the longitudinal element may permit an increased length of longitudinal element and/or a reduced total length of sleeve.

The longitudinal element may comprise a stftlness. The torque threshold may be at east parUay defined by The stiffness of the longitudir element.

Providing a longitudinal element may prevent the transmission of torque above the predetermined threshold substantially independently of the configuration of the tooL For example, where the tool is reconfigurable between the first and second configurations by an axial movement, a substantiafly nonaxial movement of at least one of the coupling portlons in response to a torque above the predetermined threshold may permit the coupling portions to disengage irrespectlve of the axial movement.

Providing a longitudinal element configured to deflect or displace transverse to the element% longitudinal axis may permit a transverse cflsplacement of the bearing surface over a distance at a substantiafly constant resistance force (e.g. at east partially caused by a stiffness of the longitudinal element). The distance may be sufficient to permit engagement or disengagement of the coupling portions.

The longitudinal element may be connected to the body portion of the sleeve. The longitudinal element may be configured to deflect or displace relative to the body portion. The longitudinal element may be connected to a body portion of the sleeve at a first end portion. The first end portlon may be fixed to the sleeve body portion.

The longitudinal element may be unconnected at a second end portion. The second end portion may be configured to displace relative to the sleeve body portion. The bearing surface may be located at the second end portion of the longitudinal element.

Alternatively, the longitudinal element may be connected to the body portion of the sleeve at the second end portion. The second end portion may he fixed to the sleeve body portion. The bearing surface may be located at an intermediate portion of the longitudinal element between the first and second end portions.

The bearing surface may be located at a portion of the longitudinal element configured for maximum deflection or displacement at the predetermned torque.

S

The/each couphng portion may comprise a protrusion. The protrusion may extend radiafly relative to the sleeve and/or longitudin& element, The protrusion/s may comprise the bearing surface/s.

The/each coupng portion may comprise a recess, The recess/es may comprise the bearing surface/s.

One of the inner or outer coupUng portions may comprise a protrusn and the other of the outer or inner coupUng portions may comprise a corresponthng recess.

The inner and/or outer sleeve coupHng portion/s may be integrafly formed with the respective sleeve. For example, the longitudinal element may be integraDy formed with the body portion. ntegray forming the coupling portion with the &eeve may prevent or reduce stresses and/or impact and/or torque hsses and/or increase aUowable positioning and/or manufacturing tolerances. For example, an alternative sleeve with a nonntegral coupUng portion may require an interface between the sleeve and the coupng porhon, the additional interface potentiaUy influencing the absolute value and/or accuracy of the predetermined torque.

The each/sleeve may comprise a pluraty of coupling portions. For example, the/each sleeve may comprise a plurality of coupUng portions distributed around the sleeve. The pluraUty of coupng portions may be evenly distributed around a circumference of the sleeve. Providing a plurality of coupling portions may provide for a balanced transmission of torque about the central longitudinal axis.

The sleeve body portion may extend adjacent the longitudinal element. The sleeve body portion may extend in a longitudinal porUon b&ween adjacent longitudinal elements, The body portion niay be stiffer than the longitudin& &ement. The body portion may be thicker than at least a portion of the longitudin& element, The body portion may be distanced from the longitudinal element by a separation. The separation may permit movement of the longitudinal element relative to the sleeve body portion (e.g. radial deflection or deformation). The separation may be circumferential.

Alternatively, or additionally, the separation may be axial. The sleeve may be configured to disengage at the predetermined torque prior to closing of the separation by movement of the longitudinal element (e.g. deflection or deformation of the ongitudinal element). The longitudinal &ement may be sUffer in a directbn of rotafion than in the direcdon of deflection or deformation. For example, the longitudin& element may comprise a greater thickness in the direction of rotation (e.g. circumferential direction) than in the threcUon of deflecuon or deformavon. The longitudinal element may comprise a greater stiffness in a direction of rotation than in the direction of deflection or deformation. The longitudinal &ernent may comprise a greater torsional stiffness than a radial and/or an axial stiffness. The longitudinal element may comprise a greater axial sUffness than a radial stiffness. A deflection distance to engage or disengage the coupling porbon may be greater than the separation.

The sleeve body portion may be arranged axialiy adjacent the longitudinal element, The sleeve body portion may be arranged circumferentialiy adjacent the hngitudinal &ement.

The downhole tool may comprise a steerable toot The tool may be steerable by the selective transmission of torque between the inner and outer sleeve coupUng portions.

The downhole tool may comprise a drilling toot The downhoie ted may comprise a directional drilling toot The tool may comprise a longitudinal body. The longitudinal body may comprise a throughbore. The tool may comprise a downhole driVing assembly (e.g. including a bottom hole assembly wfth a drifl bit).

The downhole tool may comprise a reaming or underreaming tool.

The tool may be reconfigurable between the first and second configurations in response to a signal. The tool may be reconfigurable between the first and second configurations in response to a change in fluid pressure, The tool may be reconfigurable between the first and second configurations in response to a change in differential fluid pressure.

The/each sleeve may be configured to transmit rotation to/from an additional component. For example the sleeve may comprise an additional coupling for transmitting torque to the additional component.

The coupng arrangement may be configured to selectively transfer torque between a drling drive system and a driffing steering system.

The sleeve may comprise a mandreL The sleeve may comprise a throughbore, The torque threshold may be at east partiaUy determined by a mechanical pmperty of at least one of the sleeves or a mechanical proper' of a member connected or associated with one of the eeves, For example, the torque threshold may be at east partially determined by a strength and/or an impact resistance of a driven component.

The torque may be transmitted from a downhole source, such as a downhole motor (e.g. a fluidactuated motor). The torque may be transmitted from an uphole source, such as a surface motor (e.g. by rotation of a string or tubing). The torque may comprise an absolute torque. The torque may comprise a relative torque (e.g. a differential torque between the inner and outer sleeves).

According to an aspect of the invention there is provided a method of selectively transmitting torque between an inner sleeve and an outer sleeve of a downhole tool.

the method compri&ng: configuring the downhole tool to a first configuration wherein respective coupling portions of the inner and outer sleeves are axially misaligned to prevent transmission of torque between the inner and outer sleeves; reconfiguring the downhole tool to a second configuration wherein the respective coupling portions of the inner and outer sleeves are axially aligned to permit transmission of torque between the inner and outer sleeves; and preventing the transmission of torque above a predetermined torque threshoid when the tooi is in the second configuration.

The method may comprise engaging the coupling portions in the second configuration to transmit torque.

The method may comprise disengaging the coupling porUons at the predetermined torque.

The method may comprise reengaging the coupUng portions when the torque fSs b&ow the predetermined torque. The method may comprise automatically re-engaging the cou$ng portions when the torque fafls below the predetermined torque.

The method may comprise reconfiguring the downhole tool to a third configuration, wherein the respective coupling portions of the inner and outer sleeves are aSHy misaligned in a substantially opposite axial orientation. For example, where the outer sleeve coupling portion is axially positioned above the inner sleeve coupling portion in the first configuration, the outer sleeve coupling portion may be axiaHy positioned below the inner sleeve coupng portion in the third configuration (or vice versa).

The method may comprise reconfiguring the tool by varying a fluid pressure. For example, the tool may be reconfigured from the first configuration to the second configuration by reducing fluid pressure within the fool. Accordingly, torque may be selectively transmitted (e.g. to steer the tool) when a fluid pressure is reduced, Torque may he selectvely transmitted when less fluid and/or less fluid pressure may be requred (e.g. when an operation, such as driHing, is reduced).

The method may comprise reconfiguring the downhole tool to Ihe third configuration to establish a predetermined relative position of the outer sleeve with respective to the inner sleeve. The method may comprise resetting a datum by reconfiguring the downhole tool to the third configuration. Reconfiguring the tool to the third configuration may comprise aligning a rotatable portion with a drive portion. Reconfiguring the tool to the third configuration may comprise misaligning the rotatable portion with the drive portion by a predetermined amount. Reconfiguring the tool to the third configuration may be useful in establishing or reestablishing a predetermined relative position between selectiv&y rotatable portion/s and drive portion/s.

According to an aspect of the invention there is provided a downhole tool sleeve for transmitting torque downhole, the sleeve being coaxially mountable with a second sleeve and comprising a sleeve coupling portion for engagement with a coupring portion of the second sleeve for transmitting a torque between the sleeves; wherein the sleeve coupling portion is configured to prevent the transmission of torque above a predetermined torque Threshold.

According to an aspect of the invention there is provided a coupling arrangement for a downhole tool comprising: a rotatable inner sleeve comprising an inner sleeve couphng portion; a rotatable outer sleeve mounted coaxiay with the inner sleeve and comprising an outer &eeve couprig portion for forming an interengaging coupling arrangement with the inner sleeve coupling portion for transmitting a torque between the inner and outer sleeves; wherein the coupling arrangement is configured to prevent the transmission of torque above a predetermined torque Threshold.

The coupng arrangement may be configured to permit the transmission of torque when the torque fails below the predetermined torque threshold.

The sleeve coupng portions may be relativ&y axiafly movable. The sleeve coupling portions may he relafively axiaUy movable between a first configurauon whereby the inner and outer sleeve coupling portions are axially misaligned to prevent transmission of torque between the inner and outer sleeves, and a second configuration whereby the inner and outer sleeve coupling portions are axially aligned to permit a transmission of torque between the inner and outer sleeves.

Alternativ&y, the inner and outer sleeve coupling portions may be substantially axially fixed relative to each other. The coupling portions may be substantially permanently axially aligned.

The thol may be reconfigurable between a first configuration whereby the inner and outer sleeve coupling portions are axially niisaligned to prevent transmission of torque between the nner and outer sleeves, end a second configuration whereby the inner and outer sleeve coupling portions are axially aligned to permit a transmission of torque between the inner and outer sleeves.

According to an aspect of the invention there is provided a downhole tool comprising a coupling portion according to any of the previous aspects.

According to an aspect of the invention there is provided a directional drilng tool for use in downhole directional drilling, the directional drilling tool comprising: a drifl bit; a rotatable portion selectively rotatab!e to steer the directional driHing tool; a drive portion connected to the driil bit to rotate the drill bit; and a coupflng arrangement between the drive portion and the rotatable portion to selectively transmit torque to the rothtabie portion; wherein the coupling arrangement comprises a torque limiter.

The torque miter may prevent the transmission of torque above a predetermined torque threshold, The coupng arrangement may comprise a clutch, The coupUng arrangement may be interengaging.

The coupling arrangement may be fluid actuated. The rotatable portion may be a &eeve. The drive portion may be a sleeve. The rotatable and drive portions may be coaxiay mounted. The rotatable and drive portions may be concentricaUy mounted.

According to an aspect of the invention there is provided a method of directional driVing compd&ng: providing a directional driing tad comprising a duiV bit, a rotatable portion selectively rotatable to steer the directional driVing tool, a drive portion connected to the drUl bit to rotate the drUl bit, a coupling arrangement beeen the drive portion and the rotatable porfion to selectively transmit torque to the rotatable portion, and a torque limiter; rotatably driving the driV bit to drill a bore in a first direction; selectively coupling the drive portion to the rotatable portion; transmitting torque from the drive portion to rotate the rotatable portion to steer the drilling tool in a second direction; limiting the torque transmitted to the rotatable portion with the torque limiter.

According to an aspect of the invention there is provided a steerable downhole tool comprising: a driven portion; a rotatable portion selectively rotatable to steer the tool; a drive porUon connected to the driven porUon to rotate the driven portion; and a couphng arrangement between the ddve portion and the rotatable portion to eSectively transmit torque to the rotatabe portion; wherein the coupng arrangement compiises a torque miter, The invention indudes one or more corresponding aspects, embodiments or features hi isolation or in various combinations whether or not specificaHy stated (including claimed) in that combinafion or in isolation. For example, it wifi readfly be appreciated that lealures recited as optional with respect to the first aspect may be additionay appcahle with respect to the other aspects without the need to exphdUy and unnecessarily Ust those various combinations and permutations here (ag. the coupling portion ot one aspect may comprise features of any other aspect). Optional features as recited in respect of a method may be additionay apphcable to an apparatus; and vice versa, in addition, correspondhig means for performing one or more of the discussed

functions are also within the present disclosure.

ft will be appreciated that one or more embodimentafaspects may be useful in selectively transmitting rotation downhole and/or preventing transmission of an exces&ve torque.

The above summary is intended to be merely exemplary and nonlimiting.

3RIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention w now be described, by way of example only, with reference to the accompanying drawings, hi which: Figure 1 shows a downhole tool in accordance with a first embodiment of the invenUon; Figure 2 shows a longitudinal crosssection ct a portion of the tool of Figure 1, Figure 3 shows an axial crosssection of a portion of the tool of Figure 1; Figure 4 shows a view of an outer sleeve of the tool of Figure 1, shown in isolation; Figure 5 shows a longitudinal crosssection of a portion of a tool according to a second embodiment of the invention; Figure 6 shows an axial crosssection of a portion of the tool of Figure 5, and Figure 7 shows a view of an outer sleeve of the tool of Figure 5.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference is first made to Figure 1 of the drawings, which illustrates a dJrectional drilling tool for use in drilling a deviated bore, in accordance with an embodiment. of the present invention. The tool 10 is mounted to the lower end of a drHl string 12, formed of drill pipe sections, and inckides a mandrel 14 having a following end coupled to the drill string 12 and a ceding end coupled to a rotating stahiser 16, with a drill bit 16 being mounted to the stabiHser 16. Rotatably mounted on the mandrel 14 are a primary offset stabillser 20, an eccentdc mass 22, and a secondary concenthe stabiliser 24. Accordingly, in use, during a drilling operation, the drill string 12 is rotated from surface. which in turn rotates the mandrel 14, stabiliser 16 and drill bit 18.

However, the offset stabiliser 20, the concentric stabiliser 24 and the mass 22 are intended to remain substantially stationary in the bore, other than to advance axially with the rest of the apparatus, that is the stabilisers 20, 24 and the mass 22 do not rotate with the drill bit 15.

The tool 10 is utilised in directional drilling and permits the drill bit 18 to be directed to drill in a selected direction; to the side, upwards or downwards. This is achieved by arranging the primary offset stahiliser 20 to offset the mandrel 14, and thus the drill bit 18, in the bore towards the desired drilling direction. The desired offset or orientation of the stabiliser 20 is maintained by coupling the stabillser 20 to the mass 22. which features a centre of gravity spaced from the mandrel axis, such that the mass 22 tends to lie towards the ow side of the bore. The weight of the mandr& 14. drill string 12, and any apparatus and tools mounted on the drill string 12. similarly contribute to maintaining the desired offset of the stabiliser 20.

The orientation of the offset provided by the stabiliser 20, and thus the drilling direction.

may be vaded by changing the relative orientation of the stabiliser 20 and the mass 22.

This variation in orientation of the offset stabiheer 20 is achieved by means of a drive assembly 26 which may he configured such that rotation of the drill string 12 and mandrel 14 is selectively translated to rotation of the stabiliser 20 relative to the mass 22. The offset stabiliser 20 can effectively generate a three point arc when viewing a longitudinal profile, with the offset stabiliser 20 providing a middle point of contact with the bore wall between other points of contact with the drill bit 18 and the concentric stabiliser 24. Accordingly, the drill bit 18 can he angled relative to the longitudinal axis of the drill string. The angle of deviation can be predetermined by the relative axial positioning of the stahiUsers 20, 24 and the drifi bit; and by the amount of offset of the stabWser 20. For example, the angle may provide for a deviation of 3 degrees per 100 feet (30 metres) Reference wifi now be made to Figures 2 through 4 of the drawings, which iHustrate the drive assembly 26 of the tool of Figure 1 in greater detall. Reference is first made to Figure 2 of the drawings, which illustrates the relative positioning of the eiements of the drive assembly 26 with the tool inactive (e.g. not pressurised, or in a third configuration), with the relative locations of the stabillser 20 and mass 22 fixed and the mandrel 14 rotating freely relative to the stabfliser 20 and mass 22. The figure illustrates the mandrel 14 passing through the assembly 26, which includes stabiser sSves 20a, 20b forming part of the stabiHeer 20, an offset stabillser siceve housing 21. and a mass sleeve 22a which is coupled to the mass 22.

The drive assembly 26 includes the eiernents of the drive, including an inner drive ring 44 and outer driven gear cups 46, 48 which are rotatably coupled to the mass sleeve 22a and the stabiliser sleeve 20b, respectively. Located between the drive ring 84 and the outer driven gear cups 46, 48 is a toothed flexible gear ring 50. The drive ring 44 includes a slight ovality and the outer driven gears cups 48, 48 have a different number of inner gear teeth, such that rotation of the drive ring 44. transferred via the flexible gear ring 50, results in relative rotation of the outer driven cups 46, 48, and thus rotation of the stabuiser 20 relative to the mass 22. In the embodiment shown, the outer sleeve 63 is attached to the drive gear ring 44 with a threaded connection. The flexible gear ring 50 is mounted on the drive gear ring 44 via needle roller bearings 45.

The mass outer driven cup 46 is coupled to the mass sleeve 22a by casteflations 52, whUe the stahlliser outer drR'en cup 48 is coupled to the stabiliser sleeve 2Gb with a pin and hole arrangement 54.

In the embodiment shown, the tool 10 is reconfigurabie between a first configuration for drilling and a second configuration for orienting. The tool 10 is further reconfigurable to a third configuration for setting or resetting the tool in a predetermined neutral position (e.g. with steerable portions in predetermined alignment).

The first configuration (not shown) of the tooi 10 is a drilling configuration with an outer sleeve coupling portion with collet drive teeth 74 disengaged from an inner sleeve couphng portion with spne drive teeth 70 (e.g. axiay thsplaced for there being no drive from the inner sleeve 62 to the outer sleeve 63). In this configuration pressure drop is appfled by flowing through dribit nozzles, in the embodiment shown. The offset stabWzer housing 21 is oriented to a correct position for drilling n the desired direction (e.g. curved to the left). The mass 22 hangs on a low side ci the hole, with an orientation key iuVy out of slot and not touching an orientation ring.

The second configuration (shown in Figure 3) of the tool 10 is an orienting configuration where the teeth 70 of the inner sleeve 62 are axiay aligned with the teeth 74 of the outer sleeve 63; and is described in more detail hereinafter.

The third configuration of Figure 2 can be used for the tool 10 at rest, such as supplied to a rigsite. The third configuration can be used to reset Ic tool 10 to a known position of the offset stabilizer 20. For example, in the third configuration, the offset stabilizer 20 may be aligned with the mass 22. Aooordingly, the third configuration can provide a datum position downhole, where a position of the mass 22 (e.g. low side of hole) is known and a position of the offset stabilizer 20 is known r&ative to the mass 22.

Accordingly, the third configuration can provide a datum or reset configuration, if for example, there is uncertainty over a position of the offset stabiliser 20.

In the third configuration as illustrated in Figure 2, it is the intention that there shoud be no r&ative rotation between the stabiliser 20 and the mass 22. The coupling portion of spaced teeth 70 provided on the inner sleeve 62 is spaced from (e,g, downhole of) the coupling portion with corresponding teeth 72 provided on the outer sleeve 63. Similarly, in drilling mode it is the intention that there should be no relative rotation between the stabiliser 20 and the mass 22. In drilling mode, the pressure of the fluid in the mandrel bore 64 provides pressure to the piston 68, such that the inner sleeve 62 is moved uphole (to the left of the position in Figure 2) so that the spaced teeth 70 provided on the inner sleeve 82 are spaced from (e.g. uphole of) corresponding teeth 72 provided on the outer sleeve 63 (i.e. configured to a first configuration with the coupling portions axially misaligned).

When desired, rotation of the mandrel 14 is transferred to the drive ring 44 via a pressure responsive inner sleeve 62 mounted on the mandrel 14 and an outer sleeve 63 mounted coaxially with the inner sleeve 62. However, during a normal drilling operation, when the mandrel bore 64 is occupied by pressurised drilling fkiid, flthd ports 66 in the mandrel wall communicate drilling fluid pressure to a piston 68 defined by the inner sleeve 62 and urges the inner sleeve 62 into a position in which circumferentially spaced teeth 70 provided on the inner skeve 62 are spaced from corresponding teeth 72 provided on the outer &eeve 63 (La the first configuration). The teeth 72 on the outer drive sleeve 63 are provided at end portions of fingers 74, acting as collet fingers.

The lower arid of the Liner sleeve 62 features axial slots which cocperate with pins formed on the mandrel 14, and which therefore allow transfer of rotation from the mandrel 14 to the inner &eeve 62. The upper end of the inner sleeve 62 abuts, via a bearing 78, a collar 80 on the mandrel which carries a sprung pin 82. The collar 80 is urged downwardly relative to the mass sleeve 22a by a spring 84. In the first configuration, during a drHling operation, and in the presence of pressurised drilllng I ul in the mandrel bore 64, the inner sleeve 62 pushes the collar 80 upwardly against the spring 64.

When it is desired to provide relative rotation between the inner and outer sleeves 62, 63, pressure of the fluid in the mandrel bore 64 is reduced, thus reducing the pressure of the piston 68. In the absence of elevated drilllng fluid pressure, the inner sleeve 62 is urged downwards by the spring 84 to locate the inner sleeve teeth 70 in engagement with the outer sleeve teeth 72, to the second configuration of the tool 10 9as shown in Figure 3), The drive assembly 26 is thus engaged and rotation of the inner sieeve 62 will rotate the outer sleeve 63. In the illustrated embodiment the number of teeth on the drive ring 44 and driven cups 46, 48 are selected such that one hundred and twenty rotations of the mandrel 14 will produce one complete (3600) rotation of the stabiliser 20 relative to the mass 22. Accordingly, if the mandrel 14 is now rotated, the corresponding rotation of the inner sleeve 62 is transferred to the outer sleeve 63 and thus produces relative rotation of the mass sleeve 22a and the stabiliser sleeve 20b, such that the offset stabiliser 20 will rotate relative to the mass 22 with a gear ratio 120:1 reduction of speed in the embodiment shown.

Reference is now made to Figure 3, in which the tool 10 is shown in the second configuration. Figure 3 is an axial crosssection looking downhole, as indicated by the line and arrows A" in Figure 2. It is the intention that there should be relative rotation between the stabiliser 20 and the mass 22. Accordingly the inner sleeve 62 is axially aligned with the outer sleeve 63 and respective teeth 70, 72 of the inner and outer seeves 62, 63 are in contacL to transmit torque between the sleeves. In the view shown in Figure 3, the ciockwise rotation of the inner sleeve 62 is transferred to a clockwise rotation of the outer sleeve 63. The teeth 70, 72 comprise bearing surfaces 75, 77 for interengaging contact. The bearing surface 77 of the outer sleeve 63 comprises an offset angle from radiaL Accordingly a porton of the torque transferred from the bearing surface of the inner sleeve 62 is converted into a nontangential force.

The non-tangential force urges the teeth 72 of the outer sleeve 63 outwards. Whst the torque remains below a predetermined threshold, the nontanqenIial force is insufficient to move the outer teeth 72 outwards. The nontangential Force rises proportionately with the torque. At a torque threshold, the non*tangential force is sufficient to overcome the friction between the bearing surfaces 75, 77 and the stiffness of the fingers 74 such that the teeth 72 move outwards; out of engagement with the teeth 70 of the inner sleeve 62. Accordingly, the teeth 72 form a torque limiter. Accordingly, drive is no longer transmitted to the outer sleeve 63; or the drive ring 44; or the driven gear cups 48, 46; or the mass 22. The nner &eeve 62 rotates substantiay unimpeded by the outer sleeve 63, Limiting the amount of torque may prevent damage; such as to the gear teeth of either of the gear cups 46, 48.

In the embodiment shown in Figure 3, the bearing surfaces 76 of the teeth 70 of the inner sleeve 62 are substantially radiaL The respective teeth 70, 72 of the inner and outer sleeves 62, 63 can be re-engaged by reducing the torque of the inner sleeve 62 below the torque threshold. The resilience of the fingers 74 will urge the teeth 72 back into a coupling engagement with the teeth 70 of the inner sleeve 62. The inner sleeve 62 can be moved by altering the fluid pressure to prevent axial alignment if It is no longer desired to transmit torque to the outer sleeve 63.

Figure 4 shows a view of the outer sleeve 63 in isolation. The hearing surfaces 77 at the ends of the fingers 74 are shown. The fingers 74 are thinner than a body portion 79 of the seeve 63. The hoes on the end face are to house dowel pins and coi springs.

The bearing surfaces 77 are the angied faces on the sides of the four casteilations protruding into the centre of the sleeve 63. In the embodiment shown, the drive side is only ever on one side of the teeth 72 as all rotation of the main mandrel 14 is clockwise looking downhole, The straight collet fingers 74 are bent outwards radially and slightly sideways as torque is applied. The fingers 74 are de&gned to disengage the teeth 72 from teeth 70 of the inner sleeve 62 before the fingers 74 close up gaps 81 between the fingers 74 and the body portion 79.

The fingers 74, teeth 72, bearing surfaces 77, and body porhon 79 are all integraily formed. In the embodiment shown, the teeth 72 are configured to disengage at a maximum torque of 50 tHbs for a 4 %" downhole apphcation. In alternative embothments, the maximum torque may be varied. For example, for a 6 1/? appilcation, the maximum torque may be 100 ¶ibs.

Figure 5 shows a longitudinal cros&-secbon of a portion of a tool 110 accorthng to a second embodiment of the invention. The tool 110 is generafly similar to that shown in Figure 1, and as such like components share like reference numerals, incremented by 100. Accordingly, the tool 110 comprises an inner sleeve 162 and an outer sleeve 163.

It will be appreciated that the tool 110 may be incorporated in a drill string similarly to the tool 10 shown in Figure 1; and comprise a similar arrangement of stahilisers (not shown in Figure 5).

The fingers 174 are circumferentially arranged around the outer sleeve 163.

Accordingly, the outer sleeve 163 of Figure 5 is axially shorter than the outer sleeve of Figure 1, as can be seen comparing Figure 5 to Figure 2. The portion of the tool 110 shown in Figure 5 is generally similar and in a similar configuration to that shown in Figure 2.

Reference is now made to Figure 6, in which the tool 110 is shown in a second configuration. Figure 6 is an axial crosssection coking downhole, as indicated by the Une and arrows "B" in Figure 5. The teeth 170, 172 of the respective inner and outer sleeves 162, 162 are axially Signed. However, the teeth 170, 172 are shown with a small circumferential separation to aid clarity. To transmit torque, the inner sleeve 162 is rotated further clockwise into engagement with the teeth 172 of the outer sleeve 163.

In the view shown in Figure 6, the clockwise rotation of the nner sleeve 162 is transferred to a clockwise rotation of the outer sleeve 163. The teeth 170, 172 comprise bearing surfaces 175, 177 for interengaging contact. The bearing surfaces 177 of the outer sleeve 179 comprise an offset angle from radial In the embodiment shown, the bearing surfaces 175 of the teeth 170 of the inner sleeve 162 comprise an offset angle, which is a corresponding offset angle to the bearing surfaces 177 of the teeth 172 of the outer sleeve 163. As with the embodiment of Figure 3, a portion of the torque transrerred from the bearing surface 175 of the inner &eeve 162 is converted into a nontangential force in the teeth 172 of the outer sleeve 163; and, at a torque threshold, the non$angential force is suffident to overcome the friction between the bearing surfaces 175, 177 and the sfiffness of the flngers 174 such that the teeth 172 move outwards; out of engagement with the teeth 170 of the inner sleeve 162.

Accordingly, the coupUng arrangement of the bearing surfaces 175 of the teeth 170 of the inner Save 162 and the bearing surfaces 177 of the teeth 172 of the outer sleeve 163 form a torque limiter, Accordingly, drive is no anger transmitted to the outer sleeve 163; or the drive ring 144; or the driven gear cups 148, 146; or the mass 122.

The inner sleeve 162 rotates substantialiy unimpeded by the outer sleeve 163.

flgure 7 shows a view of the outer sleeve 163 of the tool of Figure 5; generally similar to the view of the outer sleeve 63 of Figure 4. The fingers 174, teeth 172, hearing surfaces 177, and body portion 179 are all integrally formed. In the embodiment shown, the teeth 172 are configured to disengage at a maximum torque alSO ff4bs, for a 4%" downhole application.

It wifi be appreciated that any of the aforementioned apparatus may have other functions in addition to the mentioned functions, and that these functions may be performed by the same apparatus.

The applicant hereby discloses in isolation each indMdual feature described herein and any combination of two or more such features, to the extent that such lectures or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and whout limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. It should be understood that the embodiments described herein are merely exemplary and that various modifications may be made thereto without departing from the scope of the invention. For example, it will be appreciated that where an outer sleeve is shown with radially movable teeth, in alternative embodiments an inner sleeve may comprise radialiy movable teeth.

Simary, where the nner Seeve s shown as being axafly movabEe, fri other ernbothments, the outer ificeve may be axafly movabe; or the seeves may be rSUvey axefly fixed. ft wU aLso be appredated, that where shown here wfth a concentdc stabser downhoe of the mass, n aRernatve embodiments aftemnalive arrangements may be provided (eg. wfth an aternafive or additbn offset stabser/s above and/or b&ow the mass). Simar1y, where shown here wfth both axaEy and radaHy msahgnabLs coupUn.g porU.ons, ft wll be appreciated that n other embociments ony one degree of misaUgnment may he requbnd. For exampe, n some appflcatbns, t may not be necessary to s&ecthe&y trarismft torque such that ony one misagnment of a torque mfter may be reqthred.

Claims

CLAIMS: 1. A downhole tool comprising: a rotatable inner sleeve comprising an inner sleeve coupng pardon; a rotatable outer sleeve mounted coaxiay with the inner sleeve and comprising an outer sleeve coupng pordon for engagement with the inner &eeve coupHng porfion for transmitting a torque between the inner and outer &eeves; wherein the tool is recontigurable between a first configuration whereby the inner and outer sleeve coupflng portions are axiaHy misagned to prevent transmission of torque between the inner and outer sleeves, and a second configuration whereby the inner and outer sleeve coupng portions are axiaUy ahgned to permit a transmission of torque between the inner and outer sleeves; and whereTh at least one of the inner or outer sieeve coupling portions is configured to prevent the transmission of torque above a predetermined torque threshold when the tool is in the second configuration.
2. The downhole tool of aim 1, wherein at east one of the inner or outer &eeve coupling portions is configured to prevent engagement of the coupling portions above the predetermined torque threshold.
3. The downhole tool of claim I or 2. wherein at east one of the inner or outer sleeve coupling portions is configured to disengage the other of the outer or inner &eeve coupling portion at the predetermined torque threshold,
4. The downhole tool of any preceding claim, wherein the inner and outer sleeve coupng portions form an interengaging coupling arrangement for transmitting the torque between the inner and outer sleeves.
5. The downhole tool of any preceding claim, wherein at least one of the inner or outer sleeve coupling portions is configured to convert at least a portion of the torque into a directional force in a direction other than that of rotation.8. The downhole tool of claim 5, wherein the directional force comprises a disengaging force at a predetermined magnitude.7. The downhoe too of any preceding dam, wherein the/each coupUng portion comprises a bearing surface for contacting the other coupng portion to transfer torque between the sleeves.8. The downhoe too of cbim 7, wherein the/each bearing surface is arranged at an offset angle.9. The downhoe tool of cEaim 7 or 8, wherein the bearing surfaces comprise a friction property such that the bearing surfaces sde r&ative to each other at the predetermined torque.10. The downhole tool of any precedir.g daim, wherein at east one of the coupng portbns comprises a longftudinal element, at least a portion of the longitudinal element being configured to deflect or displace in a substantiay nonaxial direction relative to the sleeve.11. The downhole tool of claim 10, wher&n the longitudinal element is configured to defiec or displace such that the coupng portions disengage at the predetermined torn ue.12 The downhole tool of claim 10 o 11, wherein the longitudinal element is resi lent.13. The downhole tool of any of claims 10 to 12, wher&n the longitudinal element is hngftudinaHy arranged.14. The downhole tool of any of claims 10 to 12, wherein the longitudinal element is substantiafly circumferentiay arranged.15. The downhole tool of any of claims 10 to 14, wherein the torque threshold is at least partiaUy defined by a stiffness 01 the longitudinal element.16. The downhole tool of any preceding claim, wherein the sleeve coupiLng portions are integrafly formed with the respective sleeves.17. The downhole tool of any preceding daim. wherein the inner and/or outer sleeve comprises a pluraHty of coupng portions distributed around the sleeve, 18. The downhole tool of any preceding claim, wherein the longitudinal element is connected to a body portion of the sleeve, the body portion being distanced from the longitudinal element by a separation to permit movement of the longituthnal element relative to the sleeve body portion, and wherein the sleeve is configured to disengage at the predetermined torque prior to closing of the separation by deflection or deformation of the longitudinal element, 19, The downhole tool of any preceding claim, wheren the downhole tool comprises a drflling tool.20. The downhole tool oF any preceding claim, wherein the coupling arrangement is configured to selectively transfer torque between a drilling drive system and a drilling steering system.21. A meihod of selectiv&y transmitting torque between an inner sleeve and an outer sleeve of a downhole tool, the method comprising: configuring the downhole tool to a first configuration wherein respective coupling portions of the inner and outer sleeves are axially misaligned to prevent transmission of torque between the inner and outer sleeves; reconfiguring the downhole tool to a second configuration wherein the respective coupling portions of the inner and outer sleeves are axially ahgned to permit transmission of torque between the inner and outer sleeves; and preventing the transmission of torque above a predetermined torque threshold when the tool is in the second configuration.22. The method of claim 21, wherein the method compdses engaging the coupling portions in the second configuration to transmit torque.23. The method of claim 21 or 22, wherein the method comprises disengaging the couphng portions at the predetermined torque threshold, 24. The method of any of claims 21 to 23, wherefrt the method comprises re engaging the coupng portions when the torque faUs below the predetemiined torque threshold.25. A coupUng arrangement for a downhole tooi comprising: a rotatable inner sleeve comprising an inner sleeve coupUng porfion; a rotatable outer sleeve mounted coaxy with the inner sleeve and comprising an outer sleeve coupng portion for forming an interengaging coupng arrangement with the inner sleeve coupUng portion for transmitting a torque between the inner and outer sleeves; wherein the coupling arrangement is configured to prevent the transmission of torque above a predetermined torque threshokt 26. The coupng arrangement of Sim 25, wherein the sleeve couping portions are relatively axieHy movable between a First configuration whereby the inner and outer sleeve coupng portions are Sally misaUgned to prevent transmission of torque between the inner and outer sleeves, and a second configuration whereby the inner and outer sleeve coupling portions are axiaHy agned to permit a transmission of torque between the inner and outer sleeves.27. The coupUng arrangement of claim 25, wherein the &eeve coupling portions are substantially axiauy fixed r&ative to each other.28. A directional drilUng tool for use in downhole directional drUling, the directional drifling tool comprising: a drill bit; a rotatable portion selectiveiy rotatabe to steer the directional drilling tool; a drive portion connected to the driU hit to rotate the drUl bit; and a coupling arrangement between the drive portion and the rotatable portion to selectively transmit torque to the rotatable porton; wherein the coupling arrangement comprises a torque limiter.29. The tool of claim 28, wher&n the coupng arrangement is sSectively engageable to s&ectively transmit torque to the rotatable portion.30. The tool of daim 29, wherein the couphng arrangement is fiuidactuated, such as by a drilfing fluid pressure.31. The tool of any of claims 28 to 30, wherein the rotatable portion comprises a sleeve.32. The tool of any of claims 28 to 31, wherein the drive portion comprises a &eeve.33. A method of directional driiling comprishig: providing a directional driiling tool comprising a drth hit, a rotatable portion selectiv&y rotatable to steer the directional drililng tool, a drive porUon connected to the drill bit to rotate the driil bit, a coupling arrangement between the drive portion and the rotatable portion to selectively transmit torque to the rotatable portion, and a torque iln,iter; rotatably driving the drill bit to drill a bore in a first direction; selectively coupflng the drive portion to the rotatable portion: transmitting torque from the drive portion to rotate the rotatable portion to steer the drilling tool in a second direction; limiting the torque transmitted to the rotatable portion below a predetermined torque threshold with the torque limiter.34. A downhole tool seeve for transmitting torque downhole, the sleeve being coaxially mountable with a second sleeve and comprising a sleeve coupling porilon ror engagement with a coupling portion of the second sleeve for transmitting a torque between the sleeves; wherein the sleeve coupling portion is configured to prevent the transmission of torque above a predetermined torque threshold.35. Apparatus substantially as heroin described, with reference to the figures.36. Methods substantially as herein described, with reference to the figures.